Oscillation generator



y 9 3: c. s. YERIAN 2,323,956

05 C ILLATION GENERATOR Filed Aug. 22, 1941 EIEIL'IEIEID H is Attorney Patented July 13, 1943 OSCILLATION GENERATOR Carlos S. Yerian, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application August 22, 1941, Serial No. 407,912

Claims. (Cl. 250-36) My invention relates to electron discharge oscillation generators and more particularly to such generators arranged for accurate frequency adjustment and control.

Commonly, oscillation generators arranged for accurate control of the frequency of oscillations produced employ piezoelectric crystals to efiect such control. It frequently happens, however, that the generator must be variable in frequency over a wide range, whereas piezoelectric crystals usually operate only at their natural frequency.

One of the objects of my invention is to provide an oscillation generator capable of producing oscillations continuously variable in frequency over a range but which included improved means for accurate calibration of the frequency by piezoelectric means, at one or more points in the range.

A further object of my invention is to provide an oscillation generator capable of producing oscillations variable over a wide range and which is adapted to have its frequency controlled by a piezoelectric crystal at one or more points in the range by simple operation of a switch.

The novel features which I believe to be char-' acteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which the single figure represents an embodiment of my invention.

Referring to the drawing, I have shown therein an oscillator amplifier combination comprising an electron discharge device I arranged for the generation of oscillations, which may be amplified in an electron discharge device 2 and then supplied to an output circuit connected between the anode and cathode of device 2 through terminals 3.

The electron discharge device I comprises an anode 4, a suppressor grid '5, a screen grid .6, a control electrode I, an indirectly heated cathode 8 and a heater 9 for the cathode. This heater may be energized from any suitable power supply circuit In. Connected between the control electrode I and screen grid 6 of the discharge device is an oscillatory circuit comprising an inductance II which is connected by means of switches I2 and I3 across a condenser I4 and through switches I5 and I6, across condensers I], I8, I9 and 25]. One terminal of this oscillatory circuit is connected through the usual 24 through conductor 25, and inductance coil.

26 to-the anode, and similarly, operating potential for the screen grid of the discharge device is supplied from the source 24 through conductor.

2! and switches I3 and I5 to the screen grid of the discharge device.

Bias potential for the control electrode of discharge device I and 2 may be supplied thereto over conductor 28 from resistance 29 the positive terminal of which i grounded. The potential on this resistance is such as to render devices I and 2 inoperative. This resistance is arranged to be short-circuited by telegraph apparatus such as a keying relay, or key, as conventionally indicated by the telegraph key 29, thereby to render the system operative in accordance with telegraph signals.

As thus described it will be seen that the circuits comprise those of the usual so-called Hartley oscillator and that oscillations are generated in the oscillatory circuit by reason of the interaction between the screen grid 6, acting as an anode, and the control electrode I. These oscillations are electronically coupled within the discharge device to the anode 4 thereof and excite the output circuit which comprises inductance 26 and condensers 30 and 3|. This circuit may be tuned either to the fundamental frequency to which the circuit II, I4, I1, I8, I9, 20 is tuned or it may be resonated to a suitable harmonic thereof. These oscillations are then supplied through the coupling condenser 32 to the input of an electron discharge amplifier 2 whereby they are amplified and supplied to the output circuit 3.

The frequency of the oscillations generated may be varied over a broad range by variation of the tuning condenser ll. This condenser is arranged for unicontrol with a second condenser 30 which correspondingly varies the tuning of the circuit 26,30, 3 I.

Condensers I4, I8, I9 and 20 may be the usual condensers commonly employed in such circuits and may be either fixed or variable for the purposes of initial adjustment of the system. One of these condensers, as for example the condenser 20, may be one incorporating means to maintain the frequency of the system constant irrespective of temperature variations. Such condensers are well known in the art and require no description here.

If it be desired to operate the system over different ranges of frequency, one or more additional inductances 33 may be provided and arranged to be switched into the oscillatory circuit; by means of the switches l2 and i3. Vlith this switch in the position shown the inductance H comprises the inductance of the oscillatory circuit. If this switch be operated in the counterclockwise direction, inductance il is removed from the circuit and inductance 33 substituted in its place. This inductance 33 adapts the oscillator for the generation of oscillations in a higher frequency band. Switches l2 and I3 are unicontrolled by means represented by the dotted lines 34 with an additional switch 35 in the output circuit of the discharge device I. This switch 35 is arranged to disconnect inductance 26 from the circuit and to substitute inductance 36 in its place simultaneously with the removal of inductance l I from the circuit and the substitution of inductance 33 therefor. Switches l2, l3 and 35 have six positions and may be operated counterclockwise through these positions from the position shown. The inductances IE and 33 are placed in circuit alternately, each inductance being in circuit in alternate positions of the switch. Inductances 2B, 36, 31 and 38 are selectively connected in circuit by the switch 35 to resonate with the condensers 30 and 3| at the fundamental or suitable harmonic of the frequency to which the oscillatory circuit of the oscillator resonates. Thus, while the oscillator itself operates only over two ranges of frequency the output circuit comprising condensers 30 and 3| may operate over four different ranges of frequency.

Condensers IT and 30 are arranged for unicontrol by means represented by the dotted line 40, which may comprise a rotatable shaft to which may be geared a suitable mechanism 4! for producing a continuous indication of the frequency produced at the different positions of the condenser This mechanism may comprise a series of counting devices, such as is commonly known as a Veeder counter, and which is shown, for example, in Wolff Patent No. 1,692,604, geared together and arranged to read directly in kilocycles on a number of dials the frequency of the oscillations produced and which corresponds to the particular setting of the condensers l1 and 30.

It is desirable that means be provided whereby accurate calibration of frequency at a number of points in one of the bands of frequencies produced may be readily effected. To this end a plurality of piezo-electric crystals 42, 43, 44 and 45 are provided and arranged to be connected selectively between the grid 1 and cathode 8 of the discharge device by means of the switch 22. Switch 22 is arranged for unicontrol with switches l5, l6 and 43, all of which may be operated from the position shown in the clockwise direction through a plurality of positions as shown. With the switch in the position shown, all of the crystals 42 to 45 are short-circuited by the switch 46. This expedient prevents any crystal from being excited into oscillations, when not connected in the circuit, through undesired extraneous capacity between the various conductors employed and thereby exerting undesired control of the frequency when the frequency is varied by condenser l'l through the region of proximity to the natural frequency of the crystal. This latter effect, were the crystal not short circuited, may tend to cause the frequency of the oscillator to pull in step with any crystal as the frequency is varied through the neighborhood of the natural frequency of the crystal.

When the switches are operated in a clockwise direction to the first position piezo-electric crystal 42 is connected between the control electrode 1 and the cathode of the discharge device. The connection between the grid condenser 2| and the control electrode 1 is broken by the switch 22 and the upper terminal of the condensers l! to 2B are connected through switch l6, conductor 2'! and condenser 23 to ground and to the cathode of the discharge device. The lower terminals of these condensers I! to 20 remain connected to the screen grid 6 of the discharge device. Inductance 4'! is now connected in shunt with the condensers l 1 to 20 through the switches l5 and Hi, this inductance being effectively shunted by the trimmer condenser 48, which is variable for purposes of initial adjustment.

Thus the circuit is now the conventional circuit of a crystal oscillator, the crystal 42 being connected between the control grid and cathode of the discharge device and the tuned circuit comprising condensers if, I8, l9 and 20, condenser 48 and inductance 41, all in shunt with each other, being connected between the anode and cathode of the discharge device.

This circuit H to 20, 41, 48, by reason of the insertion of the reactive elements 41 and 48, now resonates at a frequency higher than the natural frequency of the crystal by an amount sufficient to permit efficient operation of the oscillation generator at the crystal frequency and under control of the crystal.

Thus the operator having the switches in the position shown in the drawing, and desiring to produce the frequency at which the crystal 42 operates, first adjusts the condenser i7 until that frequency is read upon the dials of the indicating mechanism 4|. This frequency may be a low frequency in the band of frequencies over which the system operates when switches l2 and I3 are in the position shown. He then may operate the switches l5, I6, 22, 43 in the clockwise direction to its first position where the crystal 42 is connected between the control electrode and cathode. The oscillator then osciilates at the same frequency as before but with its frequency controlled by the crystal.

Similarly, if the operator desires to adjust the frequency to the frequency of any of the other crystals, he operates the tuning condenser until that frequency is noted on the dials of the mechanism 4|. He then throws the switch 22 to the corresponding crystal and the oscillator oscillates at the desired frequency with crystal control. Thus the operator desiring to calibrate the system may adjust it for proper operation under crystal control at the frequency determined by any of the crystals 42, 43, 44 and 45, all of which may have natural frequencies in the band over which the system operates when the switches are in the position shown. Having done this, the operator may then adjust the elements 14 and l I so that there is no change in frequency when the switch 22 is returned to the position shown. When so adjusted the system oscillates at an accurate frequency at any frequenc in the continuous band over which the sytem is tunable by means of the condenser 11.

If desired an additional reactance element corresponding to the inductance 4'! and condenser 48 may be provided for use over the band of frequencies over which coil 33 operates. This, of course, involves the use of a second set of crystals and the necessary switching means.

It will be understood that it is highly important that the oscillatory circuit be adjusted by switches l5 and It to substitute the reactance elements 41 and 48 for M and II or l4 and 33 as the case may be since if that were not done, oscillations would cease, or the system would operate unsatisfactorily, when the switch 22 is thrown to any crystal position. This is because when the crystal is connected to the discharge device the oscillating circuit is required to be tuned to a frequency higher than the natural frequency of the crystal for satisfactory operation at that frequency, and higher than the frequency at which the circuit comprising condensers l4 and I! to 2i! resonates when that circuit is adjusted to produce the natural frequency of the crystal but without crystal control.

While I have shown a particular embodiment of my invention, it will of course be understood that I do not wish to be limited thereto since different modifications may be made without departing from the spirit and scope of my invention, and I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. The combination, in an oscillation generator of an electron discharge device having input and output electrodes, a switch having a plurality 1 of positions, regenerative circuits connected to said discharge device through said switch in one position thereof and coupling said electrodes to support oscillations, said circuits including a frequency determining oscillatory circuit including a reactance element variable to change the frequency of oscillations produced over a range, a piezo electric crystal having a natural frequency in said range, said crystal being arranged to be connected to said input electrodes when said switch is operated to a second of its positions, and means responsive to operation of said switch to said second position to connect said oscillatory circuit between said output electrodes and to tune it to a frequency sufiiciently higher than the natural frequency of said crystal to support oscillations having a frequency in said range and controlled in frequency by said crystal whereby the frequency of oscillations determined by said frequency determining circuit may be compared with the frequency of oscillations controlled by said crystal by changing the position of said switch.

2. In combination, in an oscillation generator, of an electron discharge device having a cathode, anode, and control electrodes, a switch having a plurality of positions, an oscillatory circuit connected through said switch in one position thereof between said anode and control electrode to support oscillations, said circuit including a tuning condenser to vary the frequency produced over a range of frequencies, a piezo electric crystal having a natural frequency in said range, means responsive to operation of said switch to a second position to connect said crystal between said cathode and control electrodes, to disconnect said oscillatory circuit from said control electrode, to connect it between said cathode and anode and sufficiently to increase the resonance frequency thereof that when said tuning condenser is adjusted to a position corresponding to the natural frequency of said crystal oscillations of said natural frequency are produced with said switch in either said one or said second position and the frequency of oscillations produced with said switch in said two positions may be compared by operating said switch from one of said positions to the other while the position of said tuning condenser remains unchanged.

3. The combination, in an oscillation generator, of an electron discharge device having input and output electrodes, regenerative circuits coupling said electrodes to support oscillations, tuning means to vary the frequency of said oscillations over a range of frequencies, a piezo electric crystal having a natural frequency in said range, and switching means operable when said tuning means is adjusted to the frequency of said crystal to connect said crystal to said discharge device to control the frequency of oscillations produced and simultaneously to alter the tuning of said circuits to resonate at a frequency appropriately higher than the frequency produced to accommodate said crystal, whereby oscillations of the same frequency may be produced having frequency either controlled by said crystal or independent of said crystal in accordance with the operation of said switching means and the frequency of said oscillations produced without crystal control may be compared with that produced with crystal control by changing the position of said switch from one position to the other.

4. The combination, in an oscillation generator, of an electron discharge device having input and output electrodes, regenerative circuits coupling said electrodes to support oscillations, said circuits including an inductance and a condenser variable to resonate with said inductance over a range of frequency, a piezo electric crystal having a natural frequency in said range, switching means operable to connect said crystal to said discharge device to control the frequency of oscillations produced and simultaneously to disconnect said inductance and to substitute therefor reactance resonating with said condenser at a frequency such that oscillations are generated of the same frequency irrespective of the operation of said switch, whereby the accuracy of the frequency determined by said regenerative circuits may be compared by operating said switch to produce oscillations of the same frequency controlled by said crystal.

5. An oscillation generator adapted to generate oscillations continuously variable over a wide range of frequencies and arranged to be crystal controlled at a number of frequencies in said range, said generator including an electron discharge device having input and output electrodes, and a plurality of oscillatory circuits, said circuits having a variable frequency determining reactance element common thereto and having individual reactance elements, a plurality of piezo electric crystals having different natural frequencies in said range, means to connect one of said oscillatory circuits between input and output electrodes of said discharge device to generate oscillations having frequency variable over said range by variation of said common element, and means selectively to connect said piezo electric crystals to said input electrodes and simultaneously to disconnect said first connected individual reactance element and to connect a second of said individual reactance elements to said common variable reactance eledate said crystals at their respective frequencies in said range whereby the frequency in said range produced independent of said crystals may be compared with the same frequencies of oscillations controlled by respective crystals by operating said connecting means.

CARLOS S. YERIAN. 

